Figure 5. GdmHCl-induced equilibrium unfolding of OmpX^HN and OmpX^M refolded by the slow folding method.

(A) GdmHCl-induced denaturation was monitored using Trp fluorescence, and the unfolding transitions of OmpX^HN (black circles) and OmpX^M (red triangles) were fit to a two-state equation to obtain C_m. Error bars are omitted for purposes of clarity. The fits are shown as solid lines. (B) Folded (f_F) and unfolded (f_U) fractions, plotted against GdmHCl, indicate a C_m of ∼4.0 M and ∼3.6 M for OmpX^HN (black) and OmpX^M (red), respectively. Unfolding free energy (C) at various GdmHCl concentrations were linearly extrapolated to obtain ΔG^0,H2O _U in water. Thermodynamic parameters (ΔG^0,H2O _U in water, m value and C_m) derived from the equilibrium unfolding experiments are plotted in (D).